In producing deep wellbores, it is advantageous to employ a downhole, hydraulically actuated pump assembly which is simple in design, rugged in construction, and which includes a minimum number of parts, thereby achieving the advantage of a long operating time interval between pump overhauls. A pump with these desirable attributes would be expected to withstand the abuse which usually leads to early malfunction or breakage of the various component parts thereof.
In my previous U.S. Pat. No. 3,517,741, there is disclosed a pilot valve arranged eccentrically respective to the engine control valve. The present invention provides improvements in the engine and valve assembly of this and other prior art hydraulically actuated, downhole pumping systems.
In my previous U.S. Pat. No. 3,703,926, there is disclosed a downhole, hydraulically actuated pump which includes an engine and pump piston arranged with diametrically opposed faces which operate within a common fluid chamber. The present invention retains some of the advantages of this previously issued patent and additionally offers novel constructional features which overcome rod breakage in this and other prior art downhole pumps. Reference is also made to my previously issued U.S. Pat. Nos. 3,453,936; 3,625,288; and 3,865,516 for further background of this invention.
In the above referred to patents, as well as many other prior art downhole, hydraulically actuated pump systems, the length of the engine, control valve, and production pump must often attain a substantial value which contributes to rod breakage. Moreover, in many of these prior art pump assemblies, the rod which interconnects the engine and production pump pistons together is placed under tremendous tension, and this also leads to rod breakage. Accordingly, it would be desirable to provide a downhole pump assembly having all of the above attributes, while at the same time, overcoming many of the defects pointed out above, as well as other defects which may be found in many of the prior art pump assemblies.